Survivability of Apollo Abort in S-IC Phase

A documentary entitled "Apollo 11: The Untold Story," which aired on
British TV Monday night, highlighted a Bellcomm report by one J. J.
O'Connor
(http://ntrs.nasa.gov/archive/nasa/ca...1979072576.pdf)
about difficulties of safely aborting a mission during first-stage
operation. Although the documentary gave few details, O'Connor's
report clearly identifies two problems:

1. Break-up of the Launch Vehicle. During a high-Q abort, the
first-stage engines would be shut down as part of the abort procedure
The report indicates that this would cause the break-up -- and probably
explosion -- of the vehicle within half a second.
2) Break-up of the Spacecraft. Loss of one first-stage engine would
could cause the CM to separate from the SM.

The documentary implied that nothing was ever done about these problems
and that abort during the first two and a half minutes was simply
unsurvivable. Because the documentary's tone was breathless and
exaggerated, I gave little credence to this claim. To my surprise,
however, O'Connor's report does seem to have suggest that MSC may have
swept the launch-vehicle problem under the rug by simply re-defining
the acceptable abort conditions.

Was anything ever done about this?

Some of the solutions suggested were interesting. Proposals to solve
the launch-vehicle problem included commanding stage separation as part
of the abort sequence in order to achieve a relatively graceful
break-up. Another one was to keep the center F-1 engine burning during
an abort. For the spacecraft-break-up problem, *jettisoning* the
escape tower was one possibility: this apparently would have greatly
reduced the stress on the CM/SM joint. It would, of course, also have
left the crew with no escape tower!

Proponent wrote:
A documentary entitled "Apollo 11: The Untold Story," which aired on
British TV Monday night, highlighted a Bellcomm report by one J. J.
O'Connor
(http://ntrs.nasa.gov/archive/nasa/ca...1979072576.pdf)
about difficulties of safely aborting a mission during first-stage
operation. Although the documentary gave few details, O'Connor's
report clearly identifies two problems:

1. Break-up of the Launch Vehicle. During a high-Q abort, the
first-stage engines would be shut down as part of the abort procedure
The report indicates that this would cause the break-up -- and probably
explosion -- of the vehicle within half a second.
2) Break-up of the Spacecraft. Loss of one first-stage engine would
could cause the CM to separate from the SM.

Was anything ever done about this?


Henry Spencer wrote something about this in 1997
"http://yarchive.net/space/launchers/saturn_v.html"

- Ed Kyle

Ed Kyle wrote:
Proponent wrote:
A documentary entitled "Apollo 11: The Untold Story," which aired on
British TV Monday night, highlighted a Bellcomm report by one J. J.
O'Connor
(http://ntrs.nasa.gov/archive/nasa/ca...1979072576.pdf)
about difficulties of safely aborting a mission during first-stage
operation. Although the documentary gave few details, O'Connor's
report clearly identifies two problems:

1. Break-up of the Launch Vehicle. During a high-Q abort, the
first-stage engines would be shut down as part of the abort procedure
The report indicates that this would cause the break-up -- and probably
explosion -- of the vehicle within half a second.
2) Break-up of the Spacecraft. Loss of one first-stage engine would
could cause the CM to separate from the SM.

Was anything ever done about this?


Henry Spencer wrote something about this in 1997
"http://yarchive.net/space/launchers/saturn_v.html"

- Ed Kyle

The essential point is that the "High-Q" abort issue only dealt
with conditions that lasted for a few seconds, peaking during
the "Max-Q" point at about T+78 seconds. I doubt very much
that Apollo astronauts were not aware of the weaknesses of
their abort system.

- Ed Kyle

Ed Kyle wrote:
I doubt very much
that Apollo astronauts were not aware of the weaknesses of
their abort system.

And there was an auto-abort based on excessively rapid rotation, so the
abort system should fire automatically if the Saturn V started to break
up around max-Q. Of course that's no guarantee they'd survive, but it
was better than expecting the astronauts to figure out there was a
problem and fire the abort system.

Mark

In article .com,
Proponent wrote:
A documentary entitled "Apollo 11: The Untold Story," which aired on
British TV Monday night, highlighted a Bellcomm report...
(http://ntrs.nasa.gov/archive/nasa/ca...1979072576.pdf)

They really needed to talk to someone who knew more about the technical
history of the hardware... although such people are admittedly a bit
thin on the ground. :-) The report's work was done about a year before
the Saturn V first flew manned, and the hardware and procedures were
changing steadily during that time.

1. Break-up of the Launch Vehicle. During a high-Q abort, the
first-stage engines would be shut down as part of the abort procedure
The report indicates that this would cause the break-up -- and probably
explosion -- of the vehicle within half a second.

Only during the fairly-brief high-q period -- 10-20 seconds -- and only if
there were simultaneously strong bending forces imposed, e.g. from passing
through windshear.

And that's why there was an automatic abort if specified attitude rates
were exceeded (or if a double engine failure occurred) during most of the
first-stage flight.

2) Break-up of the Spacecraft. Loss of one first-stage engine
could cause the CM to separate from the SM.

Note, though, that the report says: "This is due to the fact that the
engines are not canted to go through the vehicle center of gravity since
this would significantly reduce payload capability." In fact, as flown,
the outboard engines *were* canted somewhat about 20s after liftoff,
bringing their thrust vectors closer to the center of mass, for this exact
reason. (Admittedly, you have to read some pretty obscure documents to
know about this.)

Also, the third and final cause of automatic abort was loss of electrical
continuity from IU to CM, an indication of structural failure somewhere
in between.

The documentary implied that nothing was ever done about these problems
and that abort during the first two and a half minutes was simply
unsurvivable.

Nope. See above.

In fact, there's a hint of some interesting history here. The report's
discussion of the spacecraft-breakup problem notes the possibility of
doing an automatic abort on a single engine failure, but says this "would
require a change of abort philosophy and hardware". I wonder if MSC was
previously trying for an all-manual abort system, and this was the point
where they conceded that some automatic aborts were required.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |